Spectral dependence of the refractive index of single-crystalline GaAs for optical applications

The refractive index of crystalline GaAs is measured by the method of interference refractometry in the wavenumber range from 10 500 to 540 cm-1 (or the wavelength range from 0.9 to 18.6 μm) with a resolution of 0.1 cm-1. The measurement results are approximated by the generalized Cauchy dispersion formula of the 8th power. Spectral wavelength dependences of the first- and second-order derivatives of the refractive index are calculated, and the zero material dispersion wavelength is found to be λ0 = 6.61 μm. Using three GaAs plates of different thicknesses we managed to raise the refractive index measurement accuracy up to 4 x 10-4 or 0.02%, being nearly by an order of magnitude better than the data available.